Hybrid rocket engine



fiEAHCH HUGE/'1 A ril 20, 1965 R. H. LOUGHRAN HYBRID ROCKET ENGINE FiledJune 12, 1961 IN V EN TOR. Poss/2r H. LOUGHRAA/ United States Patent3,178,885 HYBRID ROCKET ENGINE Robert H. Loughran, Redlands, CaHf.,assignor, by mesne assignments, to Lockheed Aircraft Corporation,Burbank, Calif., a corporation of California Filed June 12, 1961, Ser.No. 116,416 3 Claims. (Cl. 6035.6)

This invention relates generally to hybrid rocket motors, which term isused to describe rocket motors that use separate fuel and oxidizercomponents, one of which is liquid and the other solid. Moreparticularly, the invention is concerned with a rocket motor of thisclass which vaporizes and heats a liquid oxidizer to a high temperaturebefore contact with the solid fuel.

One of the main objects of the invention is to provide a solidpropellant ignition heater and gas generator that pressurizes a liquidoxidizer and vaporizes Tes'ime as the heater exhausts through anunderexpanded flow nozzle upon the reaction surface of the solid fuel.

Another object of the invention'is' to provide an ignition heater thatpressurizes a liquid oxidizer and vaporizes the same at a flow nozzlefor high temperature diffusion over the solid fuel react iye surface.

Still another object of the invention is to provide an igniter thatpressurizes, vaporizes and heats a liquid oxidizer to high temperaturebefore contact with the solid fuel.

A further object of the invention is to provide an ignition heater forhybrid rocket engines, which vaporizes and heats a liquid oxidizerbefore the latter contacts a solid fuel, and thus permits the use ofvarious combinations of solid fuel and liquid oxidizer, that are notnormally reactive when the oxidizeris in the liquid phase.

A still further object of the invention is to provide an ignitionheater, the high temperature combustion products of which change aliquid oxidizer to a gaseous condition and also break down the fuelcomposition to more reactive.

Yet another object of the invention is to provide an ignition heater andgas generator which vaporizes and preheats a liquid component, so thatmany combinations of liquid and solid fuel and oxidizer may be used.

Still another object of the invention is to provide a relatively simpleand low cost type of injector that insures hot gas phase reaction andhigh burning rate and at the same time has capability of Omi oifoperation \n rmal sw n- The foregoing and other objects and advantagesof this invention will be clear to those skilled in the art uponconsideration of the following detailed specification of oneillustrative embodiment thereof, reference being had to the accompanyingdrawing, in which:

FIGURE 1 is a schematic view of a hybrid rocket engine, showing apreferred form of the invention.

Referring to the drawing, which is more or less schematic, it will benoted that the various elements are not shown in complete structuraldetail. This has not been deemed necessary because it is believed that aprofusion of drawings would merely complicate the disclosure offundamental elements and the combination thereof. The prior artrecognizes certain essential elements and obviates the necessity ofengineering detail.

A solid fuel rocket motor casing of conventional design has the usualexhaust nozzle 11 at the rear end thereof. Bonded to the inner surface13 of the casing 10 is a body 12 of solid fuel which may, if desired,have some oxidizer incorporated therein. The body 12 of solid fuel has acentral, longitudinally extending bore 14 which forms the burningsurface. The bore 14 may be of circular cross-section, or it may takeany other conmake it figuration. The elements heretofore recited areentirely conventional.

Mounted on the front end of the motor casing 10 is an auxiliary gasgenerator 15 comprising a casing 16 loaded with a grain of solidpropellant 17. The solid propellant 17 differs from the solid fuel 12 ofthe motor casing 10 in one important respect, and that is that itcomprises a fuel and oxidizer mixture in proportions for stoichiometriccombustion, whereas the fuel 12 is either completely without oxidizer,or with a substantial deficiency of oxidizer, whereby combustion of thefuel 12 cannot be supported without additional oxidizer. The solidpropellant 17 is provided with a central longitudinally extending bore18 from one end of the casing 16 to the other, the rear end of said boreopening into an under-expanded nozzle 19. The nozzle 1-9 is attached tothe front end of the motor casing 10 around the marginal edges of anaperture 20, and the nozzle 19 thus discharges directly into the bore14. An igniter 21 is mounted on the front end of the casing 16, andserves to ignite the solid propellant 17 when fired. The combustiongases from the auxiliary gas generator 15 are exhausted through thenozzle 19 into the rocket engine and upon the reaction surface 14 of thefuel 12.

A pressure tube 22 is connected at 23 to the auxiliary gas generator 15,and at 24 to a container 25 filled with highly reactive liquid oxidizer26, such as chlorine trifluoride (ClF for example. A conventional piston30 with standard sealing rings 31 is disposed in the pressure end 32 ofthe casing 15. One end of a supply tube 33 is connected at 34 to thecontainer 25, and its other end communicates with a plurality of ports,or discharge openings 35, in the throat of the nozzle 19. A valve 36 isprovided in the supply tube 33 for controlling the flow of liquidoxidizer, and thereby controlling the rate of combustion of the fuel 12,which has the effect of controlling the propulsive thrust of the rocketmotor 10. Maximum rate of combustion of the fuel 12 for maximum thrustis obtained when the quantity of oxidizer 26 discharged into the bore 14is exactly equal to the requirement for stoichiometric combustion. Thethrust of the rocket motor 10 may be programmed in any desired manner bymerely operating the valve 36 to restrict the flow of oxidizer. Ifdesired, combustion of the fuel 12 may be stopped by closing the valve36, and even restarted by opening the valve again, provided theauxiliary gas generator 15 is still operating.

Operation of the invention is effected by firing the igniter 21, whichignites the small solid propellant 17 in the auxiliary gas generator 15.The combustion gases of the auxiliary gas generator are dischargedthrough the under-expanded flow nozzle 19 into the bore 14. Thus thenozzle 19 effectively becomes a heater nozzle due to the hot gasespassing therethrough. At the same time, the combustion gases of thegenerator 15 pressurize the liquid oxidizer through the tube 22, actingagainst the piston 30. The liquid oxidizer 26 controlled by the valve36, is forced through the throat holes 35 in the heater nozzle 19. Theheater nozzle gas flow vaporizes and heats the liquid oxid'uer to hightemperature before contact with the solid fuel 12. The vaporized liquidoxidizer is diffused completely within the rocket engine and over thereactive surface. The invention is characterized by insensitivity toscaling, high burning rate, and high mass ratio. There is also aninsensitivity of specific impulse to ratio of fuel and oxidizer. Therocket engine is rendered flexible and enables the use of combinationsof fuel and oxidizer that are not normally reactive when the oxidizer isin a liquid state. The hot gaseous condition of the oxidizer tends tobreak down the fuel composition to make it more reactive. Variouscombinations of conventional solid fuels, oxidized and slightlyoxidized, or solid fuels alone may be used.

In addition to the solid fuel and liquid oxidizer combination describedherein, the present invention contemplates the use of combinations ofsolid oxidizers such as ammonium nitrate, for example, and liquid fuel,such as gasoline or kerosene. In this instance, the solid oxidizer wouldbe loaded in the motor case 10, and the liquid fuel would be carried inthe container 25.

While I have shown and described in considerable detail what I believeto be the preferred form of my invention, it will be understood by thoseskilled in the art that various changes may be made in the shape andarrangement of the several parts without departing from the broad scopeof the invention as defined in the following claims.

I claim:

1. A hybrid rocket engine utilizing afuel component and an oxidizercomponent, one of said components being solid and the other beingliquid, said engine comprising a motor case loaded with said solidcomponent and having a rearwardly directed nozzle through whichcombusliquid component is contained, an auxiliary ga ge r 1e .=1. .9l f

mounted on the front end of the motor case and liavlng a nozzledischarging into said motor case, means for pressurizing said containerwith gas generated by said auxiliary gas generator, means for conveyingsaid liquid component under pressure from said container to saidlastnamed nozzle and means including said last-named nozzle for mixingsaid liquid component with the hot combustion gases discharged by saidauxiliary gas generator, whereby the said liquid component is vaporizedas it is discharged into said motor case for reaction with said solidcomponent.

2. A hybrid rocket engine comprising a motor case having a rearwardlydirected exhaust nozzle, a body of solid fuel contained within saidmotor case, said body of solid fuel defining a combustion port openingat one end into said exhaust nozzle, an auxiliary gas generator having anozzle discharging into said combustion port at the other end thereof, acontainer of liquid oxidizer, a conduit opening at one end into saidcontainer and at the other end into said last-named nozzle, and a secondconduit connecting said auxiliary gas generator with said container,whereby gas pressure developed in said generator is applied to saidcontainer, and forces said liquid oxidizer into said last-named nozzlewhere it is vaporized before being discharged into said combustion port.

3. A hybrid rocket engine as defined in claim 2, wherein said auxiliarygas generator comprises a second case loaded with solid propellant, andmeans for igniting said solid propellant.

References Cited by the Examiner UNITED STATES PATENTS 2,753,801 7/56Cumming 35.6 2,791,883 5/57 Moore et al. 6039.47 2,878,643 3/59 Fox6035.6 2,940,256 6/60 Conyers et al 60--39.48 2,972,225 2/61 Cumming eta1. 603948 2,984,973 5/61 Stegelman 6039.48 2,987,875 6/61 Fox 6035.62,996,880 8/61 Greiner 6035.6 2,998,703 9/61 Badders 6035.6 3,017,7481/62 Burnside 6035.6 3,065,597 '9 11/62 Adamson et al 6035.6 2,065,59811/62 Schultz 6035.6 3,068,641 12/62 Fox 6035.6 3,115,007 12/63 Fox6035.6

SAMUEL LEVINE, Primary Examiner. ABRAM BLUM, Examiner.

1. A HYBRID ROCKET ENGINE UTILIZING A FUEL COMPONENT AND AN OXIDIZERCOMPONENT, ONE OF SAID COMPONENTS BEING SOLID AND THE OTHER BEINGLIQUID, SAID ENGINE COMPRISING A MOTOR CASE LOADED WITH SAID SOLIDCOMPONENT AND HAVING A REARWARDLY DIRECTED NOZZLE THROUGH WHICHCOMBUSTION PRODUCTS ARE DISCHARGED, A CONTAINER IN WHICH SAID LIQUIDCOMPONENT IS CONTAINED, AN AUXILIARY GAS GENERATOR MOUNTED ON THE FRONTEND OF THE MOTOR CASE AND HAVING A NOZZLE DISCHARGING INTO SAID MOTORCASE, MEANS FOR PRESSURIZING SAID CONTAINER WITH GAS GENERATED BY SAIDAUXILIARY GAS GENERATOR, MEANS FOR CONVEYING SAID LIQUID COMPONENT UNDERPRESSURE FROM SAID CONTAINER TO SAID LASTNAMED NOZZLE AND MEANSINCLUDING SAID LAST-NAMED NOZZLE FOR MIXING SAID LIQUID COMPONENT WITHTHE HOT COMBUSTION GASES DISCHARGED BY SAID AUXILIARY GAS GENERATOR,WHEREBY THE SAID LIQUID COMPONENT IS VAPORIZED AS IT IS DISCHARGING INTOSAID MOTOR CASE FOR REACTION WITH SAID SOLID COMPONENT.